Isometric exercise ball



FIG. 1 is a front elevational view of an isometric exercise ball, embodying my new design, the rear view being identical;

FIG. 2 is a side elevational view thereof, the opposite side view being identical; and,

FIG. 3 is a top plan view thereof, the bottom plan view being identical. 

The ornamental design for an isometric exercise ball, as shown and described. 